Sometimes when you are using a MySQL InnoDB Cluster, you might encounter some performance issue because one node becomes dramatically slow.
First of all, why ? A node can apply the transactions slower than the other nodes for many different reasons. The most frequents are for example, slower disks (remember, it’s advised to have nodes with the same specifications), but if you are using a RAID controller with a BBU, during the learning cycle, the write performance can decrease by 10 or even more. Another example could be an increase of IO operations that will flood the full IO capacity of the system. Making a local backup or sharing the server resources with some other components could lead in such behavior.
To avoid to have a node lagging to much behind and try to sustain the same throughput all over the cluster, Group Replication uses a flow control mechanism ( …[Read more]